Google Translate:
The S55 engine is hot and is based on the basic features of the N55. However, the CCT is reinforced with several ribs to the higher boost pressure into account. Furthermore, other pistons, connecting rods, crankshafts, valves, valve seats, including a different injection system and a completely different principle loaders provide further differentiation! So you can already speak of a completely separate motor, which will be fitted. Performance will be about 440 hp and run tests just last vote ...

Also there is news on V6:
Some still haunts the story about, you would experience the V6 a little later.
This is not so! The V6 project with the name "Apollo" was finally closed after exactly 20 experimental units built. All derivatives M3 (Sedan, GT Coupe, grand coupe and convertible) will all be driven by one and the same S55

CONCLUSION (based on above):
So, it won't sound like a Chevy Celebrity after all?
That is a relief to me, I must admit.